The traditional duce-phase uninterrupted power supply (UPS) generally uses three-phase half budge rectifier boost topology that comprising a single battery pact which can only control the sum of voltage of positive and negative bus. In order to maintain the balance of the positive and negative bus's voltage, current technology usually adds a balancing device, as shown in FIG. 1. With the technical proposal, the cost and circuit complexity are increased, meanwhile the reliability of the boost in battery state is decreased. At the same time, the balancing device generates additional power consumption while maintain the balance of the positive and negative bus's voltage, which reduces the efficiency of the boost under battery state.
In addition, as shown in FIG. 2, the rectifier boost topology that use single battery pack with its negative pole connected with the negative pole of bus bar comprising the topology that applied to two level and three-level. However, in modular UPS, the multi module UPS needs to share the battery pack, and the positive and negative bus of each module UPS is independent. Therefore, the topology mentioned above cannot applied to modular UPS.
The modular UPS has high flexibility of power expansion and has easy online maintenance, which is the mainstream of the future development direction of high frequency UPS and has been widely used in banking, communications and data centers and other fields. As shown in FIG. 3, modular UPS is generally use three-phase positive and negative double boost rectifier boost topology that comprising dual battery pack, which can realize that multiple module share one battery pack and the positive and negative bus between different modules is independent. However, the topology just mentioned increase three inductors and three thyristor compared with the rectifier boost topology that use single battery pack.